The long term goals of this research are to ascertain similarities and differences in the etiology of hypertension for blacks and whites and to identify those biobehavioral factors which contribute to the excess risk for hypertension among black Americans. Myocardial, blood pressure, and renal responses (i.e., sodium and potassium handling) to laboratory and naturalistic stressors will be evaluated in young adult (18-22 year old) black and white males. Subjects for this study will be normotensive or will have marginally elevated resting blood pressures. Behavioral stressors will involve competitive, reaction time tasks (i.e., active coping) as well as more passive coping conditions. For each subject, data will be obtained on: 1) family history of hypertension; 2) family social class background; 3) Type A behavior, as measured by the Structured Interview; 4) propensity for anger and hostility, as measured by the Buss-Durkee Inventory; and 5) coping style, as measured by the John Henryism Scale for Active Coping. The role of the sympathetic nervous system in mediating these effects will be assessed by the use of beta-adrenergic antagonists. In subgroups of subjects, follow-up studies will evaluate blood pressure control through the assessment of sodium and potassium excretion rates, and the measurement of cardiac output and systolic time intervals. Blood pressure and heart rate reactivity will also be evaluated under field conditions so as to determine the consistency with which laboratory effects generalize to real life stress. We are specifically interested in determining to what degree familial and other psychosocial background variables relate singly, or in combination, to cardiovascular and renal responses to behavioral stressors. Moreover, we wish to determine if the observed relationships are similar for blacks and whites. Where effects are found to be stronger for blacks than whites, we shall take this as preliminary evidence of their etiologic importance in the well known excess risk for hypertension among black Americans.